The present invention relates to thin wall fasteners usable for a variety of purposes. More specifically, the present invention relates to a plug type thin wall fastener assembly utilizing a mandrel and an anchor member. The present invention is particularly suited for seismic restraint purposes and for fastening system applications used in steel stud construction.
Mounting an object to a thin wall or floor surface with a hollow space behind the wall or floor (hereafter referred to together as xe2x80x9cwallxe2x80x9d) is challenging. This is because one can not manually access the space behind the wall, and because the wall itself may not provide sufficient structure to resist the moment of a typical bolt or screw inserted therein once a load is applied to the bolt or screw.
Some prior art fasteners have attempted to overcome part of this problem by providing a means for expanding a portion of the fastener on the opposite side of the wall to prevent the fastener from pulling out of the hole in the wall into which the fastener has been inserted. Generally the wall is squeezed between a front portion of the fastener and the expanded portion of the fastener. Examples include nut and bolt arrangements, bolt and nut/washer combinations, toggle bolts, and deformable plug fasteners.
A toggle bolt is a bolt having a spring loaded expandable structure coupled to one end. The expandable structure can be collapsed so that the toggle bolt passes though a hole drilled into a wall. Once the expandable structure has passed through the hole in the wall, the expandable structure springs open. One disadvantage to such fasteners is that removing the bolt allows the expandable portion to fall to the bottom of the hollow space behind the wall. Furthermore, the expandable portion may not provide sufficient resistance to turning of the entire assembly as the bolt is tightened.
A deformable plug assembly is another type of thin wall fastener. Generally such devices comprise a plug formed as an elongate body having a central longitudinal hole, a top end, a deformable middle section and a threaded portion at the end opposite the top end. When the deformable plug assembly is placed in a hole in the wall, the screw is turned and the threaded portion moves toward the top end. The deformable portion expands to a configuration that is larger than the hole to provide clamping pressure on the back side of the wall. Such devices may include features to enhance rotational resistance to prevent the deformable plug from rotating along with the bolt. However, large fasteners, and fasteners for use with very heavy objects, may require large torquing forces to be applied to set the fasteners, and the large torquing forces required may overcome the rotational resistance features of the prior art, and in addition may crack brittle wall materials.
In a typical steel stud building, the steel studs will have some wall material placed over the steel studs to form the surface of the wall. A typical floor type used in multistory office buildings consists of concrete laid over sheets of corrugated steel. Prior art fasteners used on such concrete floors may crack the concrete when tightened. Also, the concrete may crack during seismic activity.
A typical wall material includes dry wall comprising a gypsum material sandwiched between two layers of paper. Prior art fasteners will squeeze the wall material when set, which can crack or crush the wall material, resulting in poorly set fasteners. Furthermore, seismic activity also tends to crack brittle materials such as dry wall and concrete.
What is needed is a thin wall fastener, a thin wall fastener assembly, and a method of using such thin wall fasteners that overcomes disadvantages of the prior art, that can withstand severe torquing, and that allows a bolt to be removed and replaced for affixing objects to the wall.
One embodiment of the invention is a thin wall fastener or anchoring apparatus for mounting objects to a thin wall or floor surface (hereafter xe2x80x9cwallxe2x80x9d). The anchoring apparatus is comprised of a spacer member having means for rotation encompassing an aperture, integral with an open ended cylindrically shaped shank member, integral with an open ended cylindrically shaped clinching member having means for expanding upon being compressed, integral with an open ended cylindrically shaped threaded member having internal threads. The members of the anchoring apparatus share a common central axis.
In other embodiments, the anchoring apparatus further comprises a mandrel having a head at one end with means suitable for rotation, and a cylindrical shaft extending from the head, the cylindrical shaft having an externally threaded distal end for engaging the internal threads of the anchoring apparatus. Together, the anchoring apparatus and mandrel combine to form a thin wall fastener assembly.
Additionally, the thin wall fastener assembly may further include a spanner wrench having means for preventing rotation of the anchoring apparatus, while also enabling rotation of the mandrel.